Methods to potentiate cancer therapies

ABSTRACT

Disclosed are methods for potentiating the anti-cancer properties of an anti-cancer therapy in a mammal by administering with the therapy a compound (such as relaxin or γ-IFN) that has a tissue tensile modulus-reducing property, an ability to reduce the interstitial viscosity of the cancer, an ability to increase the hydraulic conductance of the cancer, or an ability to increase collagen turnover or decrease collagen formation at or near the cancer, where the therapy and the compound are administered at dosages which together are sufficient to destroy, slow, or arrest the cancer. Also disclosed is a method for treating cancer in a mammal involving the administration of relaxin and/or γ-IFN peptides and an anti-cancer therapy to the mammal, where the peptides and the therapy are administered at dosages which together are sufficient to destroy, slow, or arrest the cancer.

This application claims the benefit of Provisional application Ser. No.60/074,502, filed Feb. 12, 1998.

BACKGROUND OF INVENTION

This invention relates to anti-cancer therapy, particularly for thetreatment of solid tumors.

Cancer accounts for one fifth of the total mortality in the UnitedStates and is the second leading cause of death. One effectiveanti-cancer therapy is chemotherapy. However, in the treatment of solidtumors (e.g., tumors in the lung, colon, and breast), efficienttreatment is hindered by the difficulty in penetrating the tumor masswith anti-cancer agents (Jain, Sci. Amer. 271: 58-65, 1994). Hence, theidentification of a means by which to facilitate the delivery oftherapeutic agents to the cancer site would enhance the effectiveness ofanti-cancer therapies.

SUMMARY OF THE INVENTION

We have discovered methods and reagents for increasing the sensitivityof cancers to therapy, and particularly chemotherapy. These methods andreagents are useful in treating cancers, particularly solid tumors.

Accordingly, in a first aspect, the invention features a method fortreating a cancer in a mammal that involves administering relaxin and ananti-cancer therapy to the mammal, the relaxin and the anti-cancertherapy being administered at dosages which together are sufficient todestroy, slow, or arrest the cancer. In various preferred embodiments ofthis aspect of the invention, the relaxin is administered either priorto the administration of the anti-cancer therapy or simultaneously withthe administration of the anti-cancer therapy. In another preferredembodiment, the method further involves administration of γ-interferon.

In a second aspect, the invention features a method for treating acancer in a mammal that involves administering γ-interferon and ananti-cancer therapy to the mammal, the γ-interferon and the anti-cancertherapy being administered at dosages which together are sufficient todestroy, slow, or arrest the cancer. In various preferred embodiments ofthis aspect of the invention. the γ-interferon is administered eitherprior to the administration of the anti-cancer therapy or simultaneouslywith the administration of the anti-cancer therapy. In another preferredembodiment, the method further involves administration of relaxin.

In preferred embodiments of both the first and second aspects of theinvention, the anti-cancer therapy includes a biotherapeutic agent, forexample, a chemotherapeutic agent. And in other preferred embodiments,the mammal is a human; and the cancer is a solid tumor, for example, asolid tumor in a tissue selected from the group consisting of brain,kidney, liver, nasopharyngeal cavity, thyroid, skin, central nervoussystem, ovary, breast, prostate, colon, rectum, uterus, cervix,endometrium, lung, bladder, pancreas, and lymph node.

In related aspect, the invention features a method for treating a cancerin a mammal that involves administering to the mammal a tissue tensilemodulus-reducing compound and an anti-cancer therapy, the compound andthe anti-cancer therapy being administered at dosages which together aresufficient to destroy, slow, or arrest the cancer.

In yet another related aspect, the invention features a method fortreating a cancer in a mammal that involves administering to the mammala compound that increases the hydraulic conductance of the cancer and ananti-cancer therapy, the compound and the anti-cancer therapy beingadministered at dosages which together are sufficient to destroy, slow,or arrest the cancer.

In a final related aspect, the invention features a method for treatinga cancer in a mammal that involves administering to the mammal acompound that increases collagen turnover or decreases collagenformation at or near the cancer and an anti-cancer therapy, the compoundand the anti-cancer therapy being administered at dosages which togetherare sufficient to destroy, slow, or arrest the cancer.

In various preferred embodiments of the above related aspects, theanti-cancer therapy includes a biotherapeutic agent, for example, achemotherapeutic agent; the mammal is a human; the cancer is a solidtumor; and the compound is either relaxin or γ-interferon, or both.

As used herein, by “cancer” or “neoplasm” is meant any abnormalproliferation of cells, which may be benign or malignant, and whichincludes solid tumors. Solid tumors may occur in a variety of tissuesincluding, without limitation, the brain, kidney, liver, nasopharyngealcavity, thyroid, skin, central nervous system, ovary, breast, prostate,colon, rectum, uterus, cervix, endometrium, lung, bladder, pancreas, andlymph node.

By “anti-cancer therapy” is meant any therapy that destroys a cancercell, or slows, arrests, or reverses the growth of a cancer cell.Anti-cancer therapies include, without limitation, radiation therapy(radiotherapy), chemotherapy, or a combination of these therapies.

By “chemotherapy” is meant the use of a chemical agent to destroy acancer cell, or to slow, arrest, or reverse the growth of a cancer cell.

By “biotherapeutic agent” is meant a substituted or unsubstitutedpeptide, polypeptide, virus cell, glycan, or combination thereof, whichmay be used to destroy a cancer cell, or to slow, arrest, or reverse thegrowth of a cancer cell.

By “chemotherapeutic agent” is meant a chemical that may be used todestroy a cancer cell, or to slow, arrest, or reverse the growth of acancer cell. Chemotherapeutic agents include, without limitation,asparaginase, bleomycin, busulfan carmustine (commonly referred to asBCNU), chlorambucil, cladribine (commonly referred to as 2-CdA),irinotecan (CPT-11), cyclophosphamide, cytarabine (commonly referred toas Ara-C), dacarbazine, daunorubicin, dexamethasone, doxorubicin(commonly referred to as Adriamycin), etoposide, fludarabine,5-fluorouracil (commonly referred to as 5FU), hydroxyurea, idarubicin,ifosfamide, interferon-α (native or recombinant), levamisole, lomustine(commonly referred to as CCNU), mechlorethamine (commonly referred to asnitrogen mustard), melphalan, mercaptopurine, methotrexate, mitomycin,mitoxantrone, paclitaxel, pentostatin, prednisone, procarbazine,tamoxifen, taxol-related compounds, 6-thiogaunine, topotecan,vinblastine, and vincristine.

By “responsive” is meant that a cell is destroyed by an anti-cancertherapy, or that the growth of a cell is slowed, arrested, or reversedby an anti-cancer therapy. The growth may be measured by any standardtechnique including, for example, cell count, measurement with calipers,or weight. Preferably, the growth of the cancer is reversed such thatthe cancer is at least 50% smaller than the cancer prior to therapy.Most preferably, the cancer is destroyed by the therapy.

By a “tissue tensile modulus-reducing compound” is meant a compound thatreduces the tensile modulus (i.e., the Young's modulus, or thecoefficient of the strain in the linear stress to strain relation) oftissue deformed by the presence of a cancer.

Other features and advantages of the invention will be apparent from thefollowing detailed description and from the claims.

DETAILED DESCRIPTION

A significant obstacle to the delivery of anti-cancer agents, andparticularly chemotherapeutic agents, to solid tumors is the tumorhydrostatic environment. The tumor core has a high internal pressure,and the tumor interstitium is highly viscous. Together these effectsform a barrier to conduction of small and large molecules from theplasma into the tumor. The high central pressure in the tumor isresisted by elastic forces generated in the surrounding tissue and fromwithin the tumor itself. Hence, the tumor generates pressure, presumablyby uncontrolled proliferation, which acts both upon the tumorconstituents and the surrounding normal but deformed tissue. Atequilibrium, the elastic forces and the pressure balance, and the tumorneither expands nor shrinks on a rapid time scale.

The elastic forces that arise by dislocation or stretching of tissuehave their origin in the strain (extension or compression) of bothintracellular cytoskeletal elements and extracellular matrix components.Together their perturbation away from an equilibrium state produces astress (force) which is usually taken to be linear in the strain. Littleis known at present about the relative contribution of intracellular andextracellular components to the Young's modulus (that is, thecoefficient of the strain in the linear stress-strain relation) oftissue deformed by the presence of a tumor (Helmlinger et al., NatureBiotechnol. 15: 778-783, 1997).

To reduce this tissue tensile modulus of solid tumors, the presentinvention involves the administration of relaxin and/or γ-interferon(γ-IFN) peptides, and thereby improves anti-cancer therapeuticapproaches. In the setting of neoplasia, a reduction in the tissuetensile modulus might be expected to facilitate tumor growth bydecreasing mechanical resistance to cellular proliferation and spread.Although superficially this would be considered undesirable, in thecontext of chemotherapy, decreased tumor pressure and facilitated tumorgrowth are expected to enhance the cytotoxic potential of existinganti-neoplastic agents, nearly all of which are directed at killingrapidly proliferating cells. With respect to relaxin, it has beendemonstrated that in at least one experimental setting, namely, thestretching of skin by an implanted subcutaneous balloon, that thepressure-volume relationship for the expansion of the fluid-filledballoon could be altered by the infusion of relaxin. In this case, theadministration of relaxin decreased the resistance to balloon expansion.Thus relaxin has, over a period of time, the capacity to decrease themodulus of skin and underlying connective tissue.

High tumor interstitial viscosity is another important consideration forthe effective delivery of chemotherapeutic agents. In general, thediffusion coefficient of molecules in liquids is inversely related tothe viscosity of the solvent. Increasing viscosity thus retardsdiffusion of plasma-borne drugs into the tumor interstitium. A recentunexpected finding has been that interstitial viscosity is stronglyinfluenced by the presence of collagen, and that infusion of collagenasedramatically facilitates penetration of small and large molecules into atumor.

Related to the high interstitial viscosity of solid tumors is a lowhydraulic conductivity. This latter measure incorporates both diffusiveand convective flow, and is a measure of total fluid conductance.Resistance to convective flow can be thought of as arising frommacroscopic effects which limit the cross-section available to flow andinduce flow resistance through propagation of the influence of thestatic boundary layer at the solid-fluid interface. Collagenasetreatment also increases hydraulic conductance, underscoring theimportance of the matrix contribution to bulk fluid flow.

The methods of the present invention further facilitate the delivery ofanti-cancer therapeutics by also reducing interstitial viscosity andincreasing hydraulic conductance of tumors through a decrease in thepresence and/or concentration of collagen. In animal models, relaxin hasbeen shown to prevent the formation of fibrotic capsules surroundingimpenetrable foreign bodies, the accumulation of collagen withinimplanted sponges, and the parenchymal fibrosis that accompaniesoxidative pulmonary damage induced by the chemotherapeutic agentbleomycin. And γ-interferon (γ-IFN), a pleiotypic cytokine produced byhelper T cells, has been shown, in a number of experimental settings, toinhibit fibroblast proliferation and associated matrix deposition,actions that are consistent with the ability of γ-IFN to antagonizeproduction of basic fibroblast growth factor (bFGF). In addition,because the mechanisms of action of these peptides differ, thecombination of relaxin and γ-IFN are likely to have more potentanti-fibrotic action than that produced by either agent alone.

The present invention makes use of these characteristics of relaxin andγ-IFN to potentiate anti-cancer therapies. Because both relaxin andγ-IFN act as anti-fibrotic agents which have the capacity to reducecollagen and matrix accumulation, and to accelerate matrix turnover,administration of these peptides are useful for reducing tumor pressureand decreasing interstitial viscosity, effects which facilitate thepenetration of cytotoxic agents into tumors. Thus, the delivery ofrelaxin, γ-IFN, or relaxin plus γ-IFN, may be utilized to potentiate theeffects of anti-cancer agents. Of the two peptides, relaxin is expectedto affect existing collagenous matrix, whereas γ-IFN is likely to retardthe formation of new tumor stroma from existing fibroblasts. As aresult, the action of relaxin is likely to be more rapid.

For cancer therapy, and particularly chemotherapy, these anti-fibroticpeptide hormones are likely to be most effective if provided in advanceof the anti-neoplastic agent, to condition the tumor bed for moreeffective drug delivery. The timing of the relaxin and/or γ-IFNtreatment should be adjusted to optimize tumor susceptibility withoutallowing excessive tumor growth. Because-relaxin is known to exert itseffects relatively rapidly (essentially immediately for protectionagainst an acute fibrotic insult), a preferable treatment regimeninvolves initiation of relaxin and/or γ-IFN treatment within a few daysprior to the first round of therapy and continuation of one or both ofthese peptides for the duration of the therapy.

CHEMOTHERAPEUTIC AGENTS

Although the administration of relaxin and/or γ-IFN may be used with anyanti-neoplastic agent, a preferred treatment regimen according to theinvention involves chemotherapy, or the use of chemical agents todestroy cancer cells. Several classes of chemotherapeutic agents areavailable, and many may be used in combination. Accordingly, it will beunderstood that where “a chemotherapeutic agent” is referred to inaccordance with the present invention, a combination of two or more suchagents may be employed. The agent(s) may be introduced into the body asa whole, or their administration may be concentrated at the tumor site.

Useful chemotherapeutic agents include, without limitation, alkylatingagents, nitrosoureas, anti-metabolites, plant alkaloids, antitumorantibiotics, and steroid hormones. Each agent is categorized accordingto its effect on the cell cycle and cell chemistry. Alkylating agents,for example, are useful chemotherapeutics that kill cells by directlyattacking DNA, and may be used, according to the invention, in thetreatment of, for example, chronic leukemias, Hodgkin's disease,lymphomas, and certain carcinomas of the lung, breast, prostate, andovary. One commonly used alkylating agent is cyclophosphamide.

Nitrosourea drugs are also useful chemotherapeutics of the inventionwhich, being able to cross the blood-brain barrier, may be used, forexample, to treat brain tumors, as well as lymphomas, multiple myeloma,and malignant melanoma. Drugs of this category, to which carmustine(BCNU) and lomustine (CCNU) belong, act similarly to akylating agentsand, additionally, inhibit changes necessary for DNA repair.

Another category of chemotherapeutics useful in the present invention isthe anti-metabolite category, which includes drugs that block cellgrowth by interfering with certain activities during the “S” phase ofthe cell cycle, usually DNA synthesis. Once ingested into the cell,anti-metabolites halt normal development and reproduction, and areuseful, for example, for the treatment of acute and chronic leukemias,choriocarcinoma, and tumors of the gastrointestinal tract, breast, andovary. Examples of commonly used anti-metabolites are 6-mercaptopurineand 5-fluorouracil (5FU).

Plant (vinca) alkaloids are plant-derived anti-tumor agents which mayalso be exploited in the methods of the invention, and includevincristine and vinblastine. These agents, which act specifically byblocking cell division during mitosis, are commonly used in thetreatment of acute lymphoblastic leukemia, Hodgkin's and non-Hodgkin'slymphomas, neuroblastomas, Wilms' tumor, and cancers of the lung,breast, and testes.

Antitumor antibiotics are another diverse group of compounds that may beused in the methods of the invention and that, in general, act bybinding with DNA and preventing RNA synthesis. These agents may be usedfor the treatment of a variety of cancers, and include doxorubicin(Adriamycin), mitomycin-C, and bleomycin.

Steroid hormones, or hormone antagonists, may also be used aschemotherapeutic agents, given their abilities to modify the growth ofcertain hormone-dependent cancers. This class includesadrenocorticosteroids, estrogens, anti-estrogens, progesterones, andandrogens. One example of a steroid hormone antagonist is tamoxifen, adrug used for estrogen-dependent breast cancer.

In addition to the above, any other chemotherapeutic agent may be usedin the methods of the invention, including other anti-neoplastic agentswhose mechanisms of action do not permit broad categorization.

Systemic Administration of Relaxin and γ-IFN

For use as enhancers of anti-cancer therapeutics, relaxin and γ-IFN maybe administered systemically, for example, formulated in apharmaceutically-acceptable buffer such as physiological saline.Preferable routes of administration include, for example, intravenous,subcutaneous, intramuscular or intradernal injections which providecontinuous, sustained levels of the drug in the patient. In otherpreferred routes of administration, relaxin and/or γ-IFN may be given toa patient by injection of a slow release preparation, slowlydissociating polymeric form, or crystalline form; this sort of sustainedadministration may follow an initial delivery of the drug by moreconventional routes (for example, those described above). Alternatively,relaxin and γ-IFN may be administered using an infusion pump, thusallowing a precise degree of control over the rate of drug release, orthrough instillation of relaxin and γ-IFN in the nasal passages in asimilar fashion to that used to promote absorption of insulin. Finally,as an alternative to nasal transmucosal absorption, relaxin and γ-IFNmay be delivered by aerosol deposition of a powder or solution into thelungs.

Local Administration of Relaxin and γ-IFN

Relaxin and γ-IFN may also be administered locally to achievesubstantial chemotherapy-enhancing outcomes. Since the desired action ofthe agent is generally upon a circumscribed mass of tissue proximal to aspecific cancer, delivery of the peptide by means which promote highlocal concentrations in the vicinity of the cancer may be especiallydesirable. For this reason, injection of the agent into tissue sitesadjacent to, or upstream of the draining circulation of, the affectedsite is preferable. Alternatively, in conditions involving deep organstructures, for example, in the displacement of tissue by invasivetumors, implantation of sustained release formulations of relaxin and/orγ-IFN (such as osmotic pumps or erodable polymeric compositionsimpregnated with the hormone) near the affected tumor site may bepreferred.

Administration of Chemotherapeutic Agents with Relaxin and γ-IFN

The most common routes of administration for chemotherapy are oral,intravenous, and intramuscular. More recently, other methods have beenused to increase the local concentration of chemotherapeutic agents at atumor site. For example, if the cancer occurs in an arm or leg.chemotlherapy may be administered by arterial perfusion, delivering thechemotherapeutic agent directly into the bloodstream of the arm or legwhere the cancer is found. Chemotherapy can also be administereddirectly into a specific cavity (intracavitary), the abdomen(intraperitoneal), the lung (intrapleural), or the central nervoussystem (intrathecal), or may be applied directly to the skin (topical).If desired, relaxin and/or γ-IFN may be administered by the same routeas the chemotherapeutic agent, even if relaxin and/or γ-IFN and thechemotherapeutic agent are not administered simultaneously.

Relaxin

Relaxin, for either systemic or local administration, may be obtainedfrom Connectics Corporation (Palo Alto, CA), or may be synthesizedeither by standard techniques of recombinant polypeptide production(see, e.g., Ausubel et al., Current Protocols in Molecular Biology, JohnWiley & Sons, New York, 1997; Sambrook et al., Molecular Cloning, ALaboratory Manual, 2nd ed., Cold Spring Harbor Press, Cold SpringHarbor, N.Y., 1989) or by peptide synthesis (e.g., by the methodsdescribed in Solid Phase Peptide Synthesis, 2nd ed., 1984 The PierceChemical Co., Rockford, Ill.). Relaxin gene and peptide sequences areprovided, e.g., in Hudson et al., Nature 301:628-631, 1983; Hudson etal., EMBO J. 3:2333-2339, 1984; and Gunnersen et al., J. Mol.Endocrinol. 15: 153-166, 1995.

Generally, the relaxin polypeptide native to a species will be preferredfor therapeutic administration. However, relaxin fragments or analogsshown to be functional, e.g., in the bioassays of Fei et al. (Biochem.Biophys. Res. Comm. 170:214-222, 1990) and Kramer et al. (In Vitro Cell.Dell. Biol. 26:647-656, 1990), and in the mouse pubic symphysis assay(Bullesbach and Schwabe, Biochemistry 25:5998-6004, 1986) are alsouseful in the invention. Particularly preferred relaxin fragmentsinclude the B29 relaxin fragment described by Winslow et al. (Proc. 71stMeeting of Endocrine Society 889 Abstract, 1989). Bryant-Greenwood, D.G., Molecular and Cellular Endocrinology 79: C125-C132, 1991), andBullesbach and Schwabe (Biochemistry 24: 7717-7722,1985). Particularlypreferred relaxin analogs include polypeptides which differ from anative relaxin polypeptide only by conservative amino acidsubstitutions, for example substitution of one amino acid for another ofthe same class (e.g., valine for glycine, arginine for lysine, asparticacid for glutamic acid, etc.). Other preferred analogs include relaxinpolypeptides which are modified for the purpose of increasing peptidestability; such analogs may contain, e.g., one or more desaturatedpeptide bonds or D-amino acids in the peptide sequence or may beformulated as cyclized peptide molecules. Finally, a prorelaxinpolypeptide (see, e.g., Hudson et al., EMBO J. 3:2333, 1984; and Vu etal., Life Sci. 52:1055, 1993) may be administered as achemotherapy-enhancing reagent according to the invention.

γ-Interferon (γ-IFN)

γ-IFN, for either systemic or local administration, may also be obtainedfrom any commercially available source (e.g., Sigma-Aldrich ChemicalCo., St, Louis, Mo.), or may be synthesized either by standardtechniques of recombinant polypeptide production or by peptidesynthesis, as described above. γ-IFN gene and peptide sequences areprovided, e.g., in Taya et al., EMBO J. 1: 953-958, 1982; Gray et al.,Nature 295: 503-508, 1982; Gray and Goeddel, Nature 298: 859-863, 1982;Devos et al., Nucleic Acids Res. 10: 2487-2501, 1982; Derynck et al.,Nucleic Acids Res. 10: 3605-3615, 1982; Gray and Goeddel, Basic LifeSci. 23: 35-61,1983; Derynck et al., Nucleic Acids Res. 11: 1819-1837,1983; Nishi et al., J. Biochem. 97: 153-159, 1985; and GenBank AccessionNo. X87308.

Generally, the γ-IFN polypeptide native to a species will be preferredfor therapeutic administration. However, γ-IFN fragments or analogsshown to be functional (using e.g., a γ-IFN functional assay such asthose described by Froyen et al., Mol Immunol 30:805-812, 1993; andSeelig et al., Biochemistry 27:1981-1987, 1988) may also be administeredas chemotherapy-enhancing reagents according to the invention. Preferredγ-IFN analogs include polypeptides which differ from a native γ-IFNpolypeptide only by conservative amino acid substitutions, and γ-IFNpolypeptides which are modified for the purpose of increasing peptidestability.

Dosages of Relaxin and γ-IFN

Relaxin is administered systemically at a dosage that provides anenhancement of the cancer cell-inhibiting effects of a chemotherapeuticagent. Dosages of relaxin are typically administered to result in ablood serum concentration that is between 0.1-100 nanograms/ml,preferably between 1-10 nanograms/ml, and may be administered with theappropriate dosage of the chemotherapeutic agent with or without γ-IFN.Because administration of the relaxin polypeptide may promote looseningof connective tissues, it may be desirable, where possible, to encouragemuscular development through physical therapy to counteract anyexcessive loosening observed during the course of relaxin treatment.

γ-IFN is also administered systemically at a dosage that provides anenhancement of the cancer cell-inhibiting effects of a chemotherapeuticagent. Dosages of γ-IFN are typically between 0.01 and 10 mg/sq. meterbody surface area (Kopp et al., J Immunother. 13: 181-190, 1993;Bolinger and Taeubel, Clin. Pharm. 11: 834-850, 1992), and may beadministered with a chemotherapeutic agent with or withoutco-administration of relaxin.

Relaxin and/or γ-IFN may be administered simultaneously with thechemotherapeutic agent or, as described above, a few days prior to theinitiation of administration of the chemotherapeutic agent. Where localadministration schemes are employed, the concentrations of relaxin inthe affected tissue may substantially exceed the levels described above.

Other Embodiments

The methods of the invention may be used to potentiate anti-cancertherapies in any mammal, for example, humans, domestic pets, orlivestock. Where a non-human mammal is treated, the relaxin and/or γ-IFNemployed is preferably specific for that species (e.g., for pigs, seeHaley et al., DNA 1: 155, 1982; and Vandenbroeck et al, Biochem.Biophys. Res. Commun. 180:1408-1415, 1991)

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindependent publication or patent application was specifically andindividually indicated to be incorporated by reference.

Other embodiments are within the claims.

What is claimed is:
 1. A method of increasing the sensitivity of amammalian solid tumor to an anti-cancer therapy, said method comprisingadministering to a mammal having a solid tumor relaxin and ananti-cancer therapy, said relaxin being administered at a dosage thatincreases the penetration of said anti-cancer therapy into said solidtumor.
 2. The method of claim 1, wherein said anti-cancer therapycomprises a biotherapeutic agent.
 3. The method of claim 1, wherein saidanti-cancer therapy comprises a chemotherapeutic agent.
 4. The method ofclaim 1, wherein said relaxin is administered prior to theadministration of said anti-cancer therapy.
 5. The method of claim 1,wherein said relaxin is administered simultaneously with theadministration of said anti-cancer therapy.
 6. The method of claim 1,wherein said method further comprises administration of γ-interferon. 7.The method of claim 1, wherein said mammal is a human.
 8. The method ofclaim 1, wherein said solid tumor is in a tissue selected from the groupconsisting of brain, kidney, liver, nasopharyngeal cavity, thyroid,skin, central nervous system, ovary, breast, prostate, colon, rectum,uterus, cervix, endometrium, lung, bladder, pancreas, and lymph node.